Laxatives · Gastrointestinal
Senna (sennosides)
sennosides · Senokot®(brand names vary by market)
The stimulant that opioid constipation actually needs.
Also: oral liquid
Mechanism
Anthraquinone glycosides activated by colonic bacteria into compounds that stimulate the myenteric plexus, increasing peristalsis and reducing water absorption.
Indications
- Constipation, particularly opioid-induced
- Bowel preparation as an adjunct
Formulations
Dosing concepts
Start with the opioid
In opioid therapy the laxative is prescribed at the same time as the analgesic, not after the constipation appears. The receptor effect in the gut does not develop tolerance.
Timing
Taken at bedtime, so it acts in the morning.
Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.
Pharmacokinetics
- Bioavailability
- Minimal systemic absorption; activated by colonic flora
- Half-life
- Acts 6 to 12 h after the dose
- Elimination
- plasma: Acts locally in the colon
Adverse effects
- Crampingcommon
- Diarrhoeacommon
- Electrolyte disturbance with prolonged heavy useserious
- Melanosis colicommonA benign brown pigmentation of the colonic mucosa seen at colonoscopy; harmless and reversible.
Contraindications & precautions
Contraindications
- Bowel obstruction
- Undiagnosed abdominal pain
- Inflammatory bowel disease flare
Precautions
- Prolonged daily use
- Dehydration
Interactions
No curated interaction entries yet for this agent.
Monitoring
Stool frequency
Titration endpoint
Whether the underlying cause is being addressed
A laxative is a symptom control, and the cause is often another drug
Counselling points
- Take it at bedtime; it usually works by morning.
- If you are on strong painkillers, keep taking this regularly rather than only when constipated.
- Cramping is common and usually means the dose can come down a little.
Clinical pearls
- Opioid constipation is a motility problem, so a stool softener alone will not fix it. The stimulant is the mechanistically correct answer and the one most often left out.
- The old teaching that stimulant laxatives cause a 'lazy bowel' has not held up; withholding them causes far more harm than using them.
References & review
- Sennosides product monograph (consult the current version for your market) (monograph)
- Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)
Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.